This application is related to another utility patent application by the same applicants, being filed concurrently, entitled xe2x80x9cOffset Cardan Gimbalxe2x80x9d.
1. Field of the Invention
The present invention, in general relates to gimbals and, more particularly, to gimbals that have a cardan assembly that is used to support and to move sensors and instrumentation about a plurality of axes.
Gimbals are commonly used to hold sensors stable when mounted on a moving vehicle, be it a land based vehicle, a sea (i.e., a water based) vehicle such as a boat or ship, or an air based vehicle such as an airplane or a helicopter.
The ability to hold a sensor stable while the vehicle moves is useful for a great variety of purposes. These purposes include obtaining information useful for navigation. Another purpose relates in general to an ability to align and then to hold the sensors where desired. Whatever information is being provided by the sensors is more reliable if the sensors themselves are held steady.
In general, gimbals have a plurality of outer axes and a plurality of inner axes. Course adjustments are commonly accomplished by movements made along the outer axes. Finer adjustments are commonly made with the inner axes.
There are a number of discreet functions a gimbal must achieve. It must both properly orient, maintain position, and support the size and weight of the sensors. This can vary from application to application.
The sensors are placed inside of a gimbal ball along with numerous other component parts that are used to orient the gimbal ball as required.
Another problem with prior art designs is supporting the weight of the sensors, also referred to as a xe2x80x9cpayloadxe2x80x9d. It is desirable to increase the effective payload of a gimbal and to better support the weight of the payload.
Gimbals include a cardan assembly that is disposed within a ball. The cardan assembly supports the weight of the payload that is carried by the gimbal as well as allowing small angular rotation in the positioning of the payload within the ball.
These changes in position are accomplished by rotating the payload (within the gimbal ball) about three axes (typical), namely elevation, roll, and azimuth. Courser adjustments are accomplished by moving the gimbal ball itself typically in two axes, elevation and azimuth.
The cardan assembly includes a cardan shaft that traverses the inside diameter of the ball. The center of the cardan shaft is used to define an internal elevation axis.
The cardan assembly must support the weight of the payload as it moves. The cardan shaft is typically supported by vibration isolators that are disposed on both ends thereof. There is a desire that the vibration isolators be as soft as possible, to better dampen the payload from vehicle fluctuations. However, a very soft isolator is subject to compression from the loading (i.e., the weight) of the payload, as well as from the magnitude of changes in loading that occur as the gimbal translates in elevation.
Therefore, a way to effectively offset the weight of the payload is desirable.
Past attempts have relied upon a spring mounted to the outer axis structure to supply a counter force upon the cardan assembly. However, these outer axis springs cause the outer axis structure to be large. This leaves less room for the gimbal ball. The space within the gimbal ball is valuable and is preferably used to optimally contain the sensors.
Furthermore, as a result of additional improvements made to gimbals by the instant applicants (see xe2x80x9cRelated Applicationsxe2x80x9d) a gimbal may now utilize an offset type of a cardan having an offset between the inner elevation axis and the outer elevation axis. The offset cardan may experience an even greater range of physical movement within the gimbal ball than do prior art designs. Accordingly, the use of spring mounted to the outer axis with an offset type of a cardan becomes increasingly impractical to utilize because a spring that must function over an even greater range of travel becomes even larger, further reducing ball volume.
Accordingly, the present disclosure relies upon an offset cardan type of a gimbal to maximally show the benefits of the instant invention. Of course, these improvements apply to and can be used with other types of gimbals (i.e., with or without an offset cardan) as well.
An offset type of a cardan assembly (with respect to the elevation axis) also allows for a physically larger payload to be carried for any given gimbal ball diameter. This potentially increases the loading upon the cardan assembly and therefore, further increases the need to provide effective support for the cardan and its payload.
It is important to understand that the internal axes provide finer corrections than do the external axes and accordingly, a smaller range of motion is therefore acceptable for movement of the payload within the gimbal ball. Larger corrections are made by moving the entire gimbal ball relative to the vehicle upon which the gimbal itself is mounted.
Ideally, for any given size of a gimbal as large and as heavy a payload as can be had is preferred as is providing the optimum support for the cardan in all of the positions that it can possibly acquire (i.e., be moved to).
It is also important to note that the cardan assembly may be used to support multiple types of sensors simultaneously. For example, a zoom television camera can be used for general spotting purposes and to locate an object of interest as well as for general pointing (i.e., aiming) of the gimbal. Upon locating the object of interest, a larger focal length camera can be used to more carefully study it. Accordingly, both types of cameras can be simultaneously mounted as part of the overall payload that is supported by the cardan assembly.
The payload may also be active instead of passive. A passive payload merely observes the object of interest whereas an active payload is adapted to affect it. The payload may be used to support an active component that can, for example, illuminate the object. For example, a gimbal can contain a source of illumination, such as a spotlight or a laser, and be mounted on, for example, a helicopter. Accordingly, as the helicopter hovers and fluctuates in its position relative to the object, the gimbal can be used to compensate for any movement by the helicopter in order to hold the source of illumination constantly upon the object.
If the source of illumination is a spotlight, then a larger and heavier payload capacity allows for a larger and brighter spotlight to be used. The same benefits apply if any other type of an active (or passive) payload is utilized.
Another problem is that when larger changes occur in elevation, these changes are made about an external or outer elevation axis. It is difficult to keep the direction of support provided to a cardan shaft normal with respect to a deck of an air vehicle to which the gimbal is attached. It is the deck of the air vehicle that is the important plane of reference, but local apparent gravity is generally perpendicular to the deck of the vehicle as is known to those possessing ordinary skill in the design of gimbals.
Furthermore, for any given weight of a payload it is desirable that the vibration isolators be as soft as is possible. A very soft vibration isolator provides optimum isolation of the payload.
Accordingly, there exists today a need for a cardan support that affords relief regarding any of the aforementioned prior art limitations.
Clearly, such an apparatus would be useful and desirable.
2. Description of Prior Art
Gimbals are, in general, known. While the structural arrangements of the known types of devices, at first appearance, may have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.
It is an object of the present invention to provide a cardan support that provides a gimbal having an improved ability to maintain (i.e., hold) sensors in proper alignment with their intended object of interest.
Still yet another object of the invention is to provide a cardan support that provides a gimbal having a greater payload capacity.
It is a first continuing object of the present invention to provide a cardan support that includes a gimbal that has an offset between the outer elevation axis and the inner elevation axis that is useful in increasing payload weight
It is a second continuing object of the present invention to provide a cardan support that includes a gimbal that has an offset between the outer elevation axis and the inner elevation axis that is useful in increasing payload volume.
It is a third continuing object of the present invention to provide a cardan support that is adapted for use with either passive or active types of payloads.
It is a fourth continuing object of the present invention to provide a cardan support that more effectively supports the weight of a payload.
It is a fifth continuing object of the present invention to provide a cardan support that is adapted to support the weight of a payload by supplying a counter force that is normal to the deck of the vehicle to which the gimbal is attached.
It is a sixth continuing object of the present invention to provide a cardan support that is adapted to support the weight of a payload by supplying a counter force that is normal to the deck of the vehicle to which the gimbal is attached while the gimbal ball moves about an outer elevation axis.
It is a seventh continuing object of the present invention to provide a cardan support that allows for the use of softer vibration isolators.
It is an eighth continuing object of the present invention to provide a cardan support that provides support to offset the local gravitational load of the sensors.
It is a ninth continuing object of the present invention to provide a cardan support that provides a method to maintain support for the gravitational load of the sensors in a normal attitude regardless of the orientation of the gimbal including that of the vehicle upon which it is mounted.
It is a tenth continuing object of the present invention to provide a cardan support that includes passive vibration isolators.
It is an eleventh continuing object of the present invention to provide a cardan support that improves the performance of a passive vibration isolator.
It is a twelfth continuing object of the present invention to provide a cardan support that includes a passive vibration isolator that supports the static weight of a payload.
It is a thirteenth continuing object of the present invention to provide a cardan support that includes mounting a vibration isolator on a rotational bearing so that an isolator assembly is adapted to rotate.
It is a fourteenth continuing object of the present invention to provide a cardan support that includes a support spring.
It is a fifteenth continuing object of the present invention to provide a cardan support that includes a cardan crane support.
It is a sixteenth continuing object of the present invention to provide a cardan support that allows selection for component parts thereof from the group of constant force springs, torsionally sprung spools, dual material rubber isolators, and non-symmetrical shapes to optimally support the weight of the payload.
It is a seventeenth continuing object of the present invention to provide a cardan support that uses an active system to support and to align a counter balancing force with respect to a payload.
It is a eighteenth continuing object of the present invention to provide a cardan support that uses a passive system to support and align a counter balancing force with respect to a payload that includes either a gear, cam, or belt drive to control the orientation of the counter balancing force.
Briefly, A cardan support structure for a gimbal that is constructed in accordance with the principles of the present invention has a cardan assembly that is used to support and move a payload. The cardan assembly includes a cardan shaft that extends across the inside of a gimbal ball, the center of which defines an inner elevation axis. The cardan assembly includes an inner azimuth axis, and an inner roll axis, about which the payload is adapted to rotate. Disposed on each end of the cardan shaft is a cardan support crane. A cardan support spring is connected at one end to each of the cardan support cranes and to each end of the cardan shaft at a remaining end. Each cardan support crane is driven by movement of the ball relative to an outer elevation axis. On one side of the cardan, an outer elevation drive motor moves the ball relative to an outer axis structure (i.e., a yoke) which in turn moves the cardan support crane on that side. Movement of the ball similarly moves the cardan support crane on the opposite side so that each of the cardan support cranes is held normal with respect to a deck of a vehicle upon which the gimbal is mounted. An alternative placement for the spring in the cardan shaft is disclosed.